Soy flour tends to be a lot lower carb than regular flour, and it can be used in baking as well, though it tends to be a bit heavier, and you have to adjust your measurements accordingly (I'm sure someone else knows this a lot better than I do).

It's still carbier than, say, almond flour or soy protein isolate, but it's definitely something to have on hand, just in case.

You're right, though. Atkins baking mix is WAY over-priced, and IMO WAY over-rated.